Bump ZeroMQ and fix some Buffer deprecations

[mauricioszabo]

I found by trial and error that ZeroMQ 6 works with the latest Electron version, but unfortunately not the version that's present on this branch.

This PR bumps the version, and fixes deprecation warnings about Buffer().

[n-riesco]

Hey! Thank you for doing this. PR looks good and it only needs addressing the points below:

• remove the lockfile (I don't distibute lockfiles for libraries. Library users should carry the burden of maintaining their own. On my end, I'll make sure jmp abides by semver and update the version numbers and package.json whenever any our dependencies break semver.
• please, read https://github.com/n-riesco/jmp/blob/master/CONTRIBUTING.md#code-contributions and add yourself to AUTHORS to acknowledge the license terms.
• I know zeromq.js hasn't bumped the engine requirements, but on my side, I want to test this PR locally, because often zeromq.js's dependencies do so silently.

[mauricioszabo]

Hi, @n-riesco, sorry for the delay, kinda forgot about this PR that I opened.

So, I removed the lockfile and added myself to the authors. Now, I don't understand what the last point is, can you clarify for me please? Which engine do you mention?

And also, thanks for taking a look at this PR :).

[n-riesco]

@mauricioszabo By node engine, I mean node version. See https://docs.npmjs.com/cli/v10/configuring-npm/package-json#engines .